Proportional indicating device.



W. M. TRICK. PROPORTIONAL INDICATING DEVICE.

urmouxon FILED MAR. 20, 1913.

1,091,872, Patented Mar. 31, 1914.

WILKINS I. TRICK, OF PITTSBURGH, PENNSYLVANIA.

PBOPOBIIONAL INDICATING DEVICE.

Specification of Letters Patent.

Application filed Inch, 20, 1818. Serial No. 755,711.

To all whom it may concern:

Be it known that I, \VILmNs M. TRIoK,'a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Proportional Indicatin Devices, of which the following is a specification.

This invention relates to proportional indicating devices and ithas reference to the provision of an improved device of simple character by means of which an unknown quantity of a proportion between certain given numbers or dimensions or the like can be readily ascertained. My invention has more particular reference to the provision of an improved proportional indicating instrument for engravers, printers, and photographers, for indicating the proporgo tional dimensions 'of photo 'raphs for engravings, and the like, which are to be enlarged or reduced in size.

The foregoing, as well as such other objects as may hereinafter appear or are incident to my invention, I attain by means of a construction which I have illustrated in preferred form in the accompanying drawings wherein Figure 1 is a plan view of my improved so indicator; and Fig. 2 is a side elevation of the device.

The device comprises a plate 7 which is preferably made of sheet metal covered with enamelor other suitable coating material,

and is in the form of a sector substantially the quarter segment of a circle. sides, the plate has its edges turned down in flanges 8 which serve as a means for supporting the device on a table or desk. The

are or curved edge of the device is bent upwardly and inwardly to provide a horizontal groove or guideway 9, the ends of the guideway being closed by lugs 10 bent up from the plate. An indicator 11, preferably formed of transparent material, is pivoted to the plate at the center, 12, from which the arc is struck and the outer end projects into the guideway 9. By this construction, injury to the indicator is prevented.

The face of the plate is divided by a plurality of concentric are lines, a, which are spaced apartat equal distances, and provided with numerals-or other indices. In the particular embodiment shown, the are 65 lines indicate inches and the usual divisions thereof, and are numbered from 1, to 12, the

At the lines bein laid out on half scale. For urposes of c earness, only one space is divided into divisions less than a half inch. The indlcator 11 is divided by are lines corresponding to the lines a and bearing corresponding members. The arc lines a are divided by radial marks b denoting inches and parts of inches, each division constituting an arc of equal length on all the arcs. It

Patented Mar. 31, 1914.

will thus be seen that the one inch line is slightly greater than an inch in length, the two inch line slightly over three inches in length, and so forth.

The reduction of a photograph for an engraving will be used as a specific illustration of the operation of the device, assuming that the photo is 12 by 6 inches, and is to be reduced 1n size so that the larger dimension will be 8 inches. The device will indicate what the smaller dimension will reduce to.

The indicator is swun on its pivot until its edgeregisters with t e 8 inch mark on the 12 inch arc of the plate. The indicator scale is then read down to the 6 inch are line and the edge of the indicator will be seen to register with the 4 inch mark on the 6 inch arc line of the plate, 4 inches being the dimension sought. It will be seenthat all the other dimensions reading down the edge of the indicator are in the same proportion, namely, as 8 is to 12. This is also the case throughout the device. It will be apparent that when enlarging aphoto or the like from 8 by 4 to 12 by 6 inches, the device is operated in the same manner.

Another method of operating the instrument is as follows, taking a photo 12 by 8 inches which is to be reduced so that its 4 larger dimension will be 9 inches. The indicator is moved so that its edge registerswith the 8 inch mark on the 12 inch arc line. The indicator is then read down to the 9 inch arc line and it will be seen that its edge coincides with the 6 inch mark, 6 inches being the desired result.

The advantage of this method of reading the instrument is that the operator may not know exactly what reduction will be convenient; by placing the indicator in the position described, all of the dimensions along the edge of the indicator will be in the desired proportion, namely, as 12 is to 8, and I by reading down the indicator, the most suitable dimensions can be readily ascertained.

It will be apparent that the .device is simple in construction, is easy to manipulate,

and effects a considerable saving in time. a right line indicator pivoted at the center The variety of its uses will be clear.

What I claim is A proportional scale comprising in com- 1; 5 bination a series of equidistant concentric arcs graduated into equal arcs commencing with the same radial line having its center at the center of the said concentric arcs, the said equal arcs being equal in length to the 10 distances between the concentric arcs, and

of the said arcs and crossing the said concentric arcs.

In testimony whereof I have hereunto signed my name in the presence of the two 15 subscribed Witnesses.

VVILKINS M. TRICK. Witnesses:

LETITIA A. MYERS, ARoHWoR'rH MARTIN. 

